Friday, February 26, 1999 Published at 17:20 GMTSci/TechIron helps combat climate changeThe Southern ocean could be much more productive with the addition of ironBy Environment Correspondent Alex Kirby

Adding iron to the sea could slow down climate change, according to the first results from an international experiment. The iron encourages plankton growth and this locks up carbon dioxide.

A team of 26 scientists, including nine Britons, has spent February seeding a 55 sq km (21 sq mile) patch of the southern ocean with iron sulphate contained in slurry.

The team also includes scientists from New Zealand, Australia, Holland, Canada and the USA.

The British contingent, from Plymouth Marine Laboratory and the University of East Anglia, has conducted similar experiments in the equatorial Pacific.

Plankton boost

This experiment was planned to find out more whether iron can boost the growth of marine life.

The team also wanted to see if the expected growth in plankton meant a reduction in levels of carbon dioxide (CO2), the main greenhouse gas produced by human activities.

They worked from the Tangaroa, a vessel belonging to New Zealand's National Institute of Water and Atmospheric Research (NIWA).

The Tangaroa docked in Wellington on Monday. A NIWA spokesman, Dr Rob Murdoch, said that early results had shown a significant boost in plankton growth caused by the iron.

And the plankton, in turn, had absorbed much more CO2.

Cloud gases

"Not only did the numbers of phytoplankton bloom extensively, but they were also responsible for the absorption of a significant amount of CO2", Dr Murdoch said.

"The growing patch of phytoplankton also produced significant quantities of a gas [dimethyl suplhide] known to be important in cloud formation."

Dr Murdoch said the experiment "provides further evidence to support the theory that high amounts of iron in the southern ocean and low amounts of atmospheric CO2 in past ice ages are linked".

Iron could mean more food

"Higher phytoplankton growth in periods when the oceans were naturally fertilised with iron would account for lower levels of CO2 and the cooling of the earth."

NIWA said that phytoplankton's role in reducing the build-up of atmospheric CO2 was thought to be as important as that of terrestrial forests and grasslands.

The team on the Tangaroa had to contend with 55 knot (80 k/ph) winds and 10m (33 feet) waves during the experiment.

They also released sulphur hexafluoride, an inert tracer dye, to help them to follow the iron as it spread over 150 sq km (58 sq miles).

A sustained and large-scale growth in plankton could have important implications for fishing, as it would mean an increase in the creatures at the bottom of the food chain.

But many scientists urge caution, pointing out that the amount of iron that would have to be thrown into the water would be stupendously large in order to have a global effect.

So the Tangaroa experiment, important as it is, is not likely on its own to provide a technological fix for escaping the results of climate change.